Interlocking system for railroads



y 1938- EC. LARRY ET AL 2,125,242

INTERLOCKING SYSTEM FOR RAILROADS Filed Nov. 27, 1931 2 Sheets-Sheet 1F'|e.1.A.

INVENTORS 9 EC Larry "4 A. Lqngdon,

THEIR ATTORNEY July 26,1938. v E. c. LARRY ET Al.

iNTERLOCKI NG SYSTEM FOR RAILROADS 2 Sheets-Sheet 2 Filed Nov 27, 1931THEIR ATTORNEY INVENTORS y W ALangdon MAE E.C.Larr

Patented July 26, 1938 PATENT OFFICE INTERLOCKING SYSTEM FOR RAILROADSEdwin 0. Larry and Andrew Langdon, Rochester,

N. Y., assignors to Company, Rochester, N. Y.

General Railway Signal Application November 27, 1931, Serial No. 577,504

16 Claims.

This'invention relates to interlocking systems for railways, and moreparticularly pertains to a system in which all of the interlockingbetween the trafiic controlling devices is accomplished by electricallyinterlocked circuits.

In one type of electric interlocking system, such as disclosed, forexample, in the prior patent of S, N. Wight, Patent No. 2,027,569, datedJanuary 14, 1936, and over which the present invention is animprovement, the route circuit portions for clearing the signal of aparticular route conform precisely with the various mechanical portionsof the track lay-out, so that as a route is set up mechanically in thetrack rails, a corresponding condition is set up electrically in theroute circuit portions.

' In accordance with the present invention, it is proposed to provide asystem of the type above outlinedin which the electrical route portionsare not completed until the locking of each of the track switchesincluded in a route is actually completed. In other words, a lock relay,which is normally energized whenever it is safe for a track switchto beoperated, but is deenergized whenever "a' track switch should bemaintained in its last operated position, is provided with backcontacts. that are included in those electrical route circuits which areassociated with those routes that may be set up over that particulartrack switch. This arrangement insures the reliability and safetyfeatures necessary for an interlocking system.

The present invention further provides approach locking with suitabletime release means associated therewith.

The present invention also provides rear re lease route locking, thatis, a particular route maybe set up with its governing signal cleared,but this route cannot be changed once a train has passed beyond thegoverning signal. However, as the train passes beyond each track switchincluded within that route, that track switch is released so as to beoperated in readiness for other routes in which it may be included.Associated with this rear release route locking is suitable releasingmeans which eliminates the time element usually required for operationof the track switch after a signal has been cleared. In other words, thepassage of a train in acceptance of a clear signaL: causes the timereleasing and approach locking-.means for that signal to be thereafterineffective until the signal lever has been manually restored to itsnormal at stop position.

Other objects, purposes and characteristic features of the presentinvention will be in part obvir ous from the accompanying drawings, andin part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to theaccompanying drawings, in which like reference characters designatecorresponding parts throughout the several views, and in which:-

Figs. 1A and 1B, when placed side by side, constitute an interlockingsystem arranged in accordance with the present invention, as applied toa simple track layout.

For the purpose of simplifying the illustration and facilitating in theexplanation thereof, the various parts and circuits constituting theembodiment of the invention have been shown diagrammatically and certainconventional illustrations have been employed, the drawings having beenmade more with the purpose of making it easy to understand theprinciples and mode of operation, than with the idea of illustrating thespecific construction and arrangement of parts that would be employed inpractice.

The various relays and their contacts are illustrated in a conventionalmanner and symbols are employed to indicate connections to the terminalsof batteries, or other suitable sources of electrical current, insteadof showing all of the wiring connections to these terminals.

The symbols and are employed to indicate the positive and negativeterminals respectively of suitable batteries, or other sources ofelectrical energy; and those circuits with which these symbols are used,are presumed to have current flowing from the positive terminaldesignated by to the negative terminal designated by If alternatingcurrent is employed, then these symbols, used to indicate the terminalsof suitable sources, will represent instantaneous relative polarities.

In the accompanying drawings, the invention has been shown applied to asimple track layout including a stretch of track having two trackswitches connecting diverging routes thereto; but

it should be understood that the invention is not Apparatus The tracklayout includes a stretch of track which for convenience in describingthe present invention, is divided into five track sections, namely,track sections 3, 5, 1, E and l l. The track section 5 is shown asincluding a suitable railroad track switch 5T5 which serves to connect aturn-out track to the main track; and similarly thetrack see-tion 9includes a suitable railroad track switch ETS which serves to connectanother turn-out track to the main track.

The switches 5TS and 9TS are preferably operated by suitable switchmachines 5SM and SSM respectively to normal and reverse positions. Theseswitch machines may be of any suitable type, such for example asdisclosed in the patent to W. K. Howe, Patent No. 1,466,903, datedSeptember 4, 1923, and are remotely controlled by an operator, locatedin a tower, through suitable control circuits represented for thepurposes of the present disclosure by a dotted line extending from therespective switch machine to its control lever in the tower. Morespecifically, the switch machine 58M is'indicated as controlled by theswitchmachine leverSSML; and similarly the switch machine 98M isindicated as controlled by the switch machine lever 9SML, but bothof'these levers are preferably located in the same tower. The controlcircuits for these switch machine control levers with their associatedswitch machines, may be of any suitable type such as disclosed forexample in the above mentioned patent of S. N. Wight, Patent No.2,027,569, dated January 14, 1936. A control circuit of the typedisclosed in this Wight patent, which is more particularly desirable forthe system of the present invention, is of the type wherein the switchmachine responds to each operation of the switch machine control leverwhen the lock' relay for that switch machine is energized, but wheneverthe lock relay is deenergized the switch machine will not respond to itscontrol lever, nor will it respond to anew position of its control leverif the lock relay becomes energized subsequent to the actuation of theswitch machine control lever tosuch a new position. In other words, theswitchmachine control lever must be in correspondence with its switchmachine, and the switch machine must be unlocked at the time of theoperation of the control lever .in'order for the switch machine torespond. Also, any oper ation of the switch machine initiated prior tothe deenergization of the lock relay is completed although the lockrelay may under certain circumstances becorne deenergizedwhile theswitch machine is still in mid-stroke.

Although various signal arrangements might be provided for the tracklayout chosen for the embodiment of the present invention, only a signalI governing trafiic in an east bound direction over the main track,signals 2-2A-2B and a signal 4 governing trafic in a west bounddirection over the main track and the two turnout tracks, have beenshown. These signals are indicated as being of the light signal type,but

may be of any other type, or any other suitable signalling means,governed in accordance with the present invention by signal leverslocated in the tower.

In actual practice some of the signalling relays, devices and the like,may be located along the trackway while other devices are located in theoperators tower,,but forconvenience in describing the present invention,it is assumed that the control levers for the switches'and signals andtheir various associated controlling circuits and relays are located inthe tower, and that suitable control. circuits are provided forredesignated by the preceding numeral.

motely connecting the tower with the traific controlling devices. is tobe understood of course that any suitable distribution of the apparatusmay be made without affecting the system of the present invention in itsoperation and usefulness.

The control levers are preferably mounted upon a suitable control panelwith indicating lamps, miniature track switches located on a trackdiagram and such other sundry devices which may be associated with sucha control panel to facilitate in the handling of traflic. A controllever ISGL is provided for governing the signal I; while a signalcontrol lever ZSGL is provided for governing the signals 2, 2A and 2B.

The condition of occupancy of the various track sections is repeated inthe tower by suit able track relays or track repeating relays indicatedby the letter reference character T and associated with their respectivetrack sections as The track sections into'which the track is divided bysuitable insulated joints are assumed to have track circuits of theclosed circuit type so that the track relays in'the tower are normallypicked up or energized. 7

The positionof the track switches is indicated in the tower by switchrepeating relays indicated by the letter reference characters WP andassociated with the particular track switch as indicated by thepreceding numerals. Each of these switch repeating relays WP is of thepolar-neutral type and is energized with current of a particularpolarity depending upon the particular position of itscorrespondingtrack switch and its iocked condition, and whenever a track switch isunlocked, the corresponding repeating relay is deenergized. Forconvenience, it is assumed that the track switches 5TS and STS arein'their normal positions and are locked, so as to energize theirrespective relays 5WP and 9WP with suitable potentials to actuate theirpolar contacts to right hand positions and to actuate their neutralcontacts to energized positions. Each switch repeating relay WP isprovided with two neutral repeating relays, one relay NP energized whenits relay WP indicates a normal locked position and another reiay RPenergized when its relay WP indicates a reverse locked position. Morespecifioaliy, relays 5NP and 5RP are associated with relay 5WP, andsimilarly relays SNP and SRP are associated with relay QWP'. Theserelays are employed for simplifying the'cir-; cuit selection throughcontacts which indicate the position and locked condition of theassociated track switches,but it is to be. understood that these relaysare not essential in practicing the invention;

Lever repeating relays IP and 2P are associated with their respectivesignal control levers, 'as indicated by their preceding numerals.Likewise, route relays [RR and 2BR are associated with their respectivesignal levers for indicating whether a particular route iselectricailyset up.

Relays IHR, ZI-IR, ZAHR and ZBHR are associated with their respectivesignals, as designated by the numerals preceding their referencecharacters. Each of these relays, when deenergized, causes itsassociated signal to indicate stop, but, when energized, causes itsassociated signal toindicate proceed subject to traific conditions asmay berequired in accordance with the usual practices.

7 Time element relays ITE and ZTE, preferably of the thermal type havingfront and back contacts, are employed with their signals for furnishingtime releasing means for the approach locking associated with suchsignals. These time element relays ITE and ZTE have time element stickrelays ITES and ZTES respectively for registering their energizedpositions.

A track stick repeater STPS is provided for the track section 5 inadvance of the signal l for the purpose of making that signal asemi-automatic stick signal, and also for the purpose of releasing theapproach locking under certain conditions as hereinafter pointed out. Itis of course optional whether this feature is provided for all of thesignals or not, and in the specific embodiment of the present invention,this feature has been shown in connection with only one signal but maybe applied to the other signals if desired.

Associated with each track section between opposing signals are twodirectional stick relays, one for east bound traffic and the otherfor'west bound traffic. More specifically, relays 5E8, ES and SEE areassociated with track sections 5, l

' and 9 respectively for east bound traffic; and

relays 5W8, 'IWS and SWS are associated with track sections 5, l and 9respectively for west bound traflic. These relays provide the routelocking between opposing signals and when the first directional stickrelay of a route for a particular direction is deenergized as the resultof the clearing of the starting signal for that route, each of thedirectional stick relays iinclruded within the route for that directionis caused to be deenergized, and is reenergized successively as thetrain passes through the route to provide the rear releasing for thetrack switches in the route. The directional stick relays for theopposite direction are not deenergized.

A lock relay is provided for each track switch and is controlled inaccordance with the directional stick route locking relays and the tracksection in which the switch is located. These locking relays, namely,relays ELR and SLR are associated with the signal route selectingcircuits and also with the switch machine control circuits, in such amanner as to prevent the operation of the corresponding switch machinesin response to movement of their respective control levers wheneverthese locking relays are deenergized, and in a mannerv to prevent theclearing of a signal for a route until the lock relays for all of theswitches in that route are deenergized.

It is believed that the characteristic features and purposes of thepresent invention will be best understood by giving the remainingdescription from. the standpoint of typical operations.

Operation Normal covtditions.Although the track switches are usuallyleft in their last operated positions, they have been shown as being intheir normal positions in correspondence with their respective switchmachine control levers. The signal control levers, however, are usuallyreturned to normal at stop positions, as shown, so that thecorresponding signals are displaying stop indications.

With the track sections unoccupied, the track relays are normallyenergized with their contacts picked up. With'the track relay 5Tenergized, the track repeating stick relay ETPS is energized by acircuit from through back contact I5 of relay IP, windings of relayETPS, front contact l6 of track relay 5T, to As the contacts of therelay 5TPS are picked up, a stick circuit is closed from" through frontcontact I! of track repeating stick relay STPS,

windings of relay STPS, front contact [6 of relay 5T, to

The switch repeating relays are energized in accordance with the normalpositions of their respective track switches, as above mentioned, thusenergizing their normal repeating relays NP by circuits obvious from thedrawings.

As the signal control levers ISGL and ZSGL are in their stop positions,the time element stick relays and the directional stick route relays forboth directions are picked up, thereby closing their auxiliary stickcircuits, as presently to be pointed out.

A pick-up circuit for relay ITES is closed from through back contact isof relay iHR, front contact IQ of relay 3T, windings of relay ITES, toThe stick circuit for this relay ITES is thus closed from through backcontact N3 of relay lI-IR, heating element 29 of thermal relay ITE,front contact 2! of relay lTES, windings of relay ITES, to

The pick-up circuit for the relay 5E8 is closed from through backcontact 58 of signal control relay iHR, back contact 22 of time elementrelay ITE, front contact 23 of relay ITES, back contact 24 of relay lP,front contact 25 of track relay 5T, windings of relay EES, to The stickcircuit for this relay 5E5 is closed from through back contact if? ofrelay IHR, back contact 22 of relay I'IE, front contact 23 of relayITES, back contact 24 of relay lP, front contact 26 of relay EES,windings of relay 5E8, to

The pick-up circuit for the relay HES is closed from through frontcontact 2'! of relay 5E8, 3'

front contact 28 of track relay lT, wire 2.), windings of relay l'ES, toThe stick circuit for this relay IE8 is closed from through frontcontact 2"! of relay 5E8, wire 3E3, frontcontact 3| of relay l'ES,windings of relay ES, to

In a similar manner, the relay 9E8 has a pick-up circuit closed fromthrough front contact 32 of relay l'ES, front contact 33 of track relay9T, windings of relay SES, to A stick circuit is closed from throughfront conla,

tact 32 of relay 1E5, front contact 34 of relay SES, windings of relay9E8, to

A pick-up circuit for relay ETES is closed from through back contacts35, 35 and 3i of relays 2AHR, ZBHR and 2HR. respectively, front contact38 of relay HT, windings of relay ZTES, to The stick circuit for thisrelay is closed from through back contacts 35, 36 and 3'! of relaysZAHR, ZBHR and 2BR respectively, heating element 39 of thermal relayETE, front contact 40 of relay ZTES, windings of relay ETES, to

A pick-up circuit for relay QWS is closed from through back contacts 35,36 and 3? of relays 2AHR, ZBHR, and ZHR respectively, back con-- tact 4|of relay ZTE, front contact 42 of relay ZTES, back contact 43 of relay2P, front contact 44 of relay 9T, windings of relay 9WS, to The stickcircuit for this relay 9W5 is closed from through back contacts 35, 35and 3'! of relays ZAHR, ZBHR and ZHR respectively, back contact 4! ofrelay ZTE, front contact 52 of relay ZTES, back contact 43 of relay 2P,front contact 45 of relay WS, windings of relay 9W8, to

A pick-up circuit for relay l'WS is closed from through front contact 46of relay 9W8, wire 41, front contact 43 of relay lT, windings of relay'lWS, to The stick circuit for this relay IWS is closed from throughfront contact 46 of relay SWS, wire 41, front contact 49 of relay IWS,windings of relay lWS, to

A pick-up circuit forrelay W8 is closed from (-1-), through frontcontact 50 of relay 'IWS, front contact 5i of relay 5T, windings ofrelay 5W8, to The stick circuit for this relay EWS is closed fromthrough front contact 53 of relay lWS, front contact 52 of relay 5W3,windings of relay 5WS, to

In other words, the directional stick relay at the beginning of a routeis governed in accordance with the clearing of the starting signal forthat route and the approach and time release locking associatedtherewith, While the remaining directional stick relays are governed bytheir preceding directional stick relay.

The lock relay 5LR is energized through a circuit from through frontcontact 53 of relay 5E8, front contact 54 of track relay 5T, windings ofrelay SLR, front contact 55 of relay 5W8, to

The lock relay SLR is energized through a circuit from through frontcontact 56% of relay 5E8, windings of relay SLR, front contact 51 oftrack relay 5T, front contact 58 of relay SWS, to

Establishing a route.With the system in the normal conditions aboveoutlined, the operator may govern the track switches to such newpositions as he may desire. For example, the operator may move theswitch machine control lever 5SML to its reverse dotted line positionwhich will operate the track switch 5TS to its reverse position. Thediverging route, thus established, is illustrated as having a signal 2Afor governing west bound train movements, but a signal governing eastbound traffic has been omitted for convenience.

Likewise, a diverging route may be set up by moving the switch machinelever SSML to its reverse dotted line position operating the trackswitch 9T8 to its reverse position. This diverging route is illustratedas having a signal 2B governing west bound train movements, but thesignal governing east bound train movements has been omitted for thesake of simplicity.

The track switches are responsive to their respective control leversonly when their respective lock relays LR are energized. For example, ifthe lock relay 5LR is deenergized, front contact 6B is open, thuspreventing the operation of the track switch 5T8 in response to theswitch machine lever 5SML. Similarly, if the lock'relay EJLR isdeenergized, front contact 6| is open, thus preventing the operation ofthe track switch QTS in response to the switch machine lever SSML. Theenergization and deenergization of the lock relays is dependent uponconditions explicitly explained hereinafter.

Although the various diverging routes -may have apparatus includingsignals, signal levers,

selecting circuits and the like, similar to those illustrated, it isconsidered sufficient for understanding the present invention toconsider only the establishment of a route over the main track involvingthe signals I and 2.

Let us assume for example then that the operator desires to set up aroute for the passageof a:

train in an east bound direction over the main track. To do this, hepositions the switch machine levers ESML and SSML in their normalpositions after which he moves the signal control lever ISGL to itsproceed or clear position.

With the lever ISGL in its proceed position, the relay IP is energizedby a pick-up circuit 'stick relay'5ES at open'back contact 24.

from through lever, lSGLina proceedposition, windings of relay lP,'backcontact 62 of relay IRR, to 1 g I As soon as the contacts of the'relaylPhave picked up, a stickcircuit is closed fromthroughlever I SGL in aproceed position, windingsof relay IlFLfront cont-act 63 of relay IP, to

The energization of therelay IP opens both the pick-up and stickcircuits of the directional The deenergization 'ofthe relay 5ES opensboth the pick-up and stick circuits for the relay IE8 at open frontcontact 21, which in turn opens both the pick-up and'stick circuits ofthe relay 9ES at open front contact 32. j The denergization of the relay5ES opens the energizing circuit for the lock relay 5LR allowing itscontacts to drop away; and, similarly, the deenergization of the relayQES opens the energizing circuit for the lock relay 9LR causing itscontacts to drop away.

With the relays 5LR and SLR deenergized, the respective track switches5TS and 9TS are prevented from being governed by their respectivecontrol levers 5SML and SSML.

The deenergization of the lock relays of each of the track switchesincluded in the route governed by the signal I completes its routeselecting circuit from through front contact 64 of relay 1?, windings ofrelay IRR, front contact 65 of relay 5N1, back contact 61 of relay SLR,wire 68, front contact 69 of relay 9NP, back contact 78 of relay SLR,windings of relay ZRR, back contact II of relay 2P, to The current whichflows in this route selecting circuit energizes the relays IRR and 2BRin series.

The picking up of the contact 8| of the relay 2RR opens the pick-upcircuit of the relay 2P, so that a route in the opposite directioncannot possibly be completed by movement of the lever ZSGL to a proceedposition. Should, by some coincidence, the lever ZSGL be moved to aproceed position and the relay 2P be picked up, then the potential wouldbe applied to both ends of the route selecting circuit by contacts 64and II, so that the relays IRR and ERR would not be energized, therebypreventing the clearing of either the signal I or the signal 3. Thus, adouble check is provided against the setting up of opposingroutes.

With the relays IP and IRR energized, an energizing circuit is completedfor the relay IHR from through front contact 12 of relay ETPS, frontcontact 13 of relay 5T, front contact 14 of relay IRR, front contact 15of relay IP, windings of relay IHR, front contact 76 of relay IP, to Theenergization of the relay IHR opens the energizing circuit for the redor stop indicator of signal I at back Contact TI of relay IHR, andcloses the energizing circuit for the green or proceed indicator ofsignal I. The picking up of contact l8 of relay IHR opens the pick-upand stick circuits of the relay ITES, for reasons which will be pointedout hereinafter.

It is to be noted, that a shunt circuit for relay IHR is closed throughwire I8 and back, contact 6 when the relay IP is deenergized. This is toprotect the relay IHR from crosses that might cause a false clear.

A route has thus been set up both mechanically over the track rails andelectrically through the signal route selecting circuit, in such amanner that the track switches within the route are positively lockedbefore the signal can be cleared,

The system is preferably provided with suitable approach locking andtime release means for the approach locking, if there are no trains uponthe approach section, the signal I, for example, may be putto stop atany time the operator may desire and the track switches included withinthe route may be immediately operated thereafter, as soon as the routecircuits and relays have returned to their normal condition.

For example, when the operator returns the signal lever ISGL to a stopposition, the relay IP is deenergized opening the energizing circuit forthe relay IHR at front contacts 15 and 16. The dee'nergization of therelay IHR puts the signal I to stop and closes the pick-up circuit forthe relay I TES from through back contact l8 of relay IHR, front contact19 of relay 3T, windings of relay ITES, to The energization of the relayI TES and the deenergization of the relays IHR and IP closes the pick-upcircuit for the relay 5ES (previously traced), which in turn closes thepick-up circuit for the relay IE8 at front contact 21, in turn closingthe pickup circuit for the relay QES at front contact 32. Theenergization of the relay 5E8 closes the energizing circuit for therelay 5LR at front contact 53 permitting the operation of the trackswitch 5TS by the lever 5SML. Similarly, the energization of the relayQES closes the energizing circuit for the lock relay BLR at frontcontact 56, the energization of which allows the operation of the switchSTS in response to the lever SSML.

Approach locking.Let us assume that the route is still set up over themain track for a train movement in an east bound direction, and that atrain has passed upon the track section 3 deenergizing the track relay3T. The signal I of course displays a proceed or clear indication, sothat the engineer governs his train in accordance therewith throughoutthe track section 3, and should the operator, for one reason or another,cause the signal I to display a stop indication by returning the signallever ISGL to a stop! position, the train in the track section 3 musteither be provided with sufficient time to stop in advance of the signalI, or be provided with sufficient time to enter the track section 5,where the detector, locking is made effective.

1 This predetermined time, provided for the purpose of safety, ismeasured off by the thermal relay [TE for the signal I.- Similarly, thethermal time element relay ZTE is provided for measuring off thepredetermined time for the signals 2, 2A and 2B.'

More specifically, if the operator moves the signal lever ISGLdeenergizig the relay IP and subsequently deenergizing the relay IHR,the relay I TES will not pick up as the front contact I9 of track relay3T is open, but the heating element of the thermal relay ITE isenergized through a circuit from through back contact l8 of relay IHR,heating element 20 of relay ITE, back contact 2| of relay ITES, to Aftera predetermined time has elapsed, the front contact 22 of the thermalrelay ITE closes a pickup circuit for the relay ITES from through backcontact N3 of relay IHR, front contact 22 of relay ITE, windings ofrelay ITES, to The opening of back contact 2| of relay ITES opens thelow resistance energizing circuit for the heating element 20 and closesfront contact 2| for completing the high resistance stick circuit forthe relay ITES. This stick circuit for the relay ITES does not allowsufficient current to flow to maintain the contact 22 of relay I'I'E inits actuated position, but allows the heating element 20 to cool so thatcontact 22 assumes a closed back contacting position. Thus, after apredetermined time after the closing of the front contact 23, the backcontact 22 is closed completing the pick-up circuit for the relay 5E8,as previously traced. The energization of the relay 5ES closes frontcontact 21 picking up the relay 'IES which in turn closes front contact32 and picks up the relay 9E8. The energization of the directional stickrelays. ES energizes the lock relays LR, as previously pointed out,allowing operation of the track switches 5TS and STS.

However, it is seen from the above description that such operation ofthe track switch is prevented for a predetermined time including boththe heating and the cooling times of the thermal relay ITE. Thisprovides that the thermal relay ITE is returned to its normal position,so that irrespective of the number of successive operations required ofthis relay, the total time required for a complete cycle of operation issubstantially the same.

Detector locking-.-Assume for convenience that the signal I is clear,and that the train on the track section 3 passes the signal I andproceeds onto the track section 5. This deenergizes the track relay 5Twhich opens the energizing circuit for the relay IHR at open frontcontact 73 causing the signal I to indicate stop. The deenergization ofthe track relay 5T also opens front contact 54 positively insuring thatthe lock relay SLR, can not be energized, so long as the train is on thetrack section 5, which provides the desired detector locking. Theoccupied condition of the track section 5 does not deenergize the westdirectional stick relay 5W8 at open front contact 5| by reason of itsstick circuit including front contact 52, as will be obvious from thedrawmgs.

Sectional releasing.'The deenergization of the track relay 5T, alsoopens the stick circuit of the track repeating stick relay STPS at openfront contact l6, which further opens the circuit for the relay IHR atfront contact 12. With the relay 5TPS deenergized and the relay IHRdeenergized, the relay ITES is immediately picked up through a circuitfrom through back contact I8 of relay IHR, back contact 80 of relay5TPS, windings of relay ITES, to As soon as the relay ITES is picked up,its stick circuit is closed as previously pointed out. In other words,the relay ITES is picked up by the passage of a train without requiringa time interval to be interposed after the signal I is automatically putto stop by the passage of the train.

Although the relay IE3 is deenergized and the relay ITES is energizedwith the back contact of relay I'I'E closed, the relay 5E8 is not pickedup until. the operator moves the signal level lSGL to a stop positiondeenergizing the relay IP and thereby closing back contact 24.

Even if the operator moves the lever ISGL to a stop position as soon asthe train accepts the signal I, thereby closing back contact 24 of relayIF, the relay 5ES can not be picked up by reason of open front contact25, until after the passage of the train beyond the track section 5allowing the energization of the track relay 5T.

When the train moves into the track section I and the relay ST is pickedup, then the relay 5E8 is energized through its pick-up circuit,(previously pointed out) which allows the lock relay 5LR. to beenergized. The apparatus is then conditioned so that the operator ispermitted to operate the track switch 5TSalthough the train has notfpassed entirely through the route originally set up. r v

It is noted, that the release of the section in theroute as the trainpasses beyond each particular track section is dependent upon therestoring of the governing signal control lever to its stop position.Thus, should the train pass beyond the route before this is done, thesignal I is maintained at stop becausethe relay QIPS cannotbe picked upuntil the relay IP is deenergi'zed and 'back contact I5 is closed byreason of the returnto the normal stop position of' the lever ISGL'. r r

Although the relay 5E8 is picked up with the train in the track sectioni, the relay 'IES does not pick up until aitrain has entirely passed outof-the section 1 into the section 9 closing front contact 28 included inthe pick-up circuit of the relay IES. In asimilar manner the relay 9E8is controlled through relay IE8 and is maintained deenergized until thetrain has passed into the section I I; As soon as the train is beyondthe track section 9 with the relay 9ES- picked up, the lock relay QLR isenergized permitting the operation of the track switch 9T8.

It is noted, that the directional stick relays EWS, TWS and SWS are notdeenergized upon the passage of the train through the route set up; bythe clearing of signal I. The reason for this is quite obvious, in thatit is' necessary for the directional stick relays to be deenergized inan order depending upon the direction in which the route is set up, andif the first directional stick relay for a given direction is notdeenergized, then the remaining directional stick relays for thatdirection will remain energized. This is because each directional stickrelay has ag stick circuit which shunts the associated track relaycontact.

I'IES through back contact of the relay ETPS is due to the fact thatininterlocking plants trains are required to move asclosely. together aspossible to facilitate traffic. Thus, although a train passing over thetrack switch 5T8, another train may be following closely on a cautionsignal, 'thatflis, with the home signal I at stopthe distant lsignalwill be caution, gso that the track section '3 is occupied when theoperator desires to move the track switch 5TS immediately after thepassage pf the first train. For example, one traffic movement might bean east bound train passing over the track switch 5TS in its normalposition followed by another train "The necessity for the picking of therelay held on thetrack section 3 by the signal I at stop;

until another east bound train has passed over the track switch STS inits reverse position. In this case, it would be undesirable to have=atime element retarding the movement of the-track switch 5T8 after thepassage of flie first train, as the train approaching the signal I ontrack sec-1 tion 3' is: moving on a caution signal and ispreparedto'stop with the signal I at stop. Hence, the shunting of the approachlocking by contact 80 is a distinct advantage. It is to be understood,that, although the relay 5TPS has a back contact 80 for shunting thefront contact l9 of'grelay 3T, 7 a back contact on the track relay 5Tmay be just as well employed, the relayi 5TPS being used moreparticularly for" the purpose of making the route relays, as for examplerelays IRE. and

2KB,- conform exactly to the track layout, as

signal, all of which has been omitted for the sake of simplicity, thecircuit in this case being illustrated as terminating in} the referencecharacterfX W s s Similarly, when the track switch STS is reversed, theroute relay 2BR has a circuit selec-- tion including front contact 86 ofswitch repeating relay SRP, anld thecircuit which extends from frontpoint of this contact extends through such selections as may be requiredfor this turn-out route, but is shown as terminating in the referencecharacter X 7 Irrespective of the particular route which is establishedwiththe signal lever 'ZSGL in'a clear or proceed position, the relays 2Pand 2BR, are

both energized and the particular signal cleared is dependent upon theselections for the respec-j tive signal control relays ZHR, ZAHR andZBHR; With a route set up for main line trafiicj' that is, with theswitches 5TS and QTSfin normal positions, the signal controlrelay ZHR isenergized, providing the directional stick relays have been properlydropped and the lock relays are in proper position This circuit iscompleted from through front contact 81 of relay 5T, front contact88 ofrelay 5NP, front contact 89 of relay 1T, wire 90, front contact 9| ofrelay SNP, front contact, 92 of relay 9T, front contact of relay 2BR,front contact 94 of relay 2P, windings of reIay'ZHR, front contact 95 ofrelay 21?, to

The relays 2AI-IR and ZBI-IR are selected in a similar manner, but asthese signal control relays govern divergingroute signals, theircircuits are carified through contacts as found- Thus, when the trackswitch5TS' nr LL) necessary in' connection with the diverging route.

For convenience the circuits of these relays ZAHR and ZEHR, have beenillustrated as ending in the reference characters X and X respectively.In brief, the signal controllever Z SGL accomplishes the clearing of oneof the signals 2, 2A or 2B dependent upon the route set up by the posiutioning ofthe switch igiiachine control levers.

It isnoted; that the selections for the relay IHR have not been carriedthrough switch position repeating contacts; while the selections. for

the signal control relays ZHR, ZAI-IR and ZBER have been carried throughvarious switch repeating contacts in accordance with the routes whichthey go-Ven. This selection of circuits for the signal control relays isnecessary only when the. signals, which they cgintrol, govern routeswhich have facing point switches. It' is also noted, that extended trackcircuit control for the signal control relays 2HR, ZAHR and ZBHR. isprovided,

but there are no stick track repeating relays; to

make these signals stick signals; while the signal control relay I HR isprovidedwith a track rejpeating stick; relay STPS tog'give the stickfea'-' ture, but is lacking the track circuit control for an extendeddistance beyond the track section 5. These various features are optionalwiththe particular situations to be met in practice. I

When a diverging route is setup, thedirectional stick relays associatedwith that routefforthe'particular direction to be establishedareideenergized; but for other routes not established- 75 7 the turn-outroute.

the directional stick relays for that direction remain energized. Forexample, it can be seen that when the track switch 9TS is reversed, itis unnecessary and in fact undesirable that the relay 'IWS shall bedeenergized upon the clearing of signal 23. Thus, in order that therelay 'IWS shall be maintained energized, an additional source of energyis provided from through front contact 95 of switch repeating relay 9RP,wire 91, to wire 4'! and thence through the circuits for relay TWS, asabove explained.v However, the deenergization of the relay 9WS effectsthe deenergization of the succeeding directional stick relay (not shown)for that direction on The reasons for this are evident, in that it iseasily seen that the switch 5TS may be desired for use in other routesat the time that the switch 9TS is reversed, or it may be pre-positionedfor a route also involving the switch 9T3, thereby saving time insetting up the entire route.

General summary.-The operation in general comprises the setting up ofthe route mechanically by operating the track stwitches of theinterlocking plant to such positions as desired, followed by themovement of the proper signal control lever to a clear positiondepending upon the particular route which is desired to be established.The movement of a signal lever to a ,clear or proceed position, causesthe directional stick relays for the route mechanically set up asgoverned by that signal, to be deenergized throughout the length of theroute to the opposing governing signal. The deenergization of thesedirectional stick relays causes the deenergization of the associatedlock relays for that route, thereby preventingoperation of the trackswitches. The deenergization of the lock relays in turn effects thecompletion of the electrical route selecting circuits, which allows thesignal control relays to be selected in accordance with the route thusestablished, thereby causing the signal for that route to display aproceed indication.

In other words, an interlocking system has been described which providesroute circuits corresponding to the actual track layout, which circuits,cannot be completed until each of the track switches within the rutebeing established has been locked, although such locking occurssubsequent to the movement of the corresponding signal control lever forthat route;

Each signal is preferably provided with suitable approach locking meanshaving associated therewith suitable time releasing means, as abovedescribed. Also, in accordance with the present invention, an additionalfeature is provided in that the approach locking is made ineffective inthe event that trains are closely following each other on acautionsignal.

Having thus shown and described an interlocking system as one specificembodiment of the present invention, it is desired to be understood thatthis form is selected to facilitate in the disclosure of the inventionrather than to limit the an interlocking system for railroads, a

stretch of railway track, a plurality of track switches in said stretchof railway track, signals for governing traffic in opposite directionsover said stretch of railroad track, and route means for said stretch ofrailroad track comprising, a circuit including contacts assumingpositions corresponding to the positions of said track switches, a routerelay at each end of said circuit, means for applying to said circuiteither of two polarities at each end, whereby the application of thesame polarity at both ends fails to energize said route relays, a lockcontact associated with each of said track switches said lock contactsbeing included in said circuit for allowing said circuit to be completedonly when the corresponding track switches are locked, and means forclearing said signals dependent upon the energization of said routerelays.

2. In an interlocking system for railroads, a stretch of railway track,a plurality of track switches in said stretch of railway track, signalsfor governing traflic in opposite directions over said stretch ofrailroad track, a control lever for each of said signals operable toclear or stop positions, means initiated by movement of any one of saidcontrol levers to a clear position for locking said track switchesagainst operation, a route circuit having current flowing therein onlywhen said track switches are locked and only when a signal lever ismoved to a clear position, and means for clearing the particular one ofsaid signals corresponding to the particular control lever in a clearedposition only if current is flowing in said route circuit.

3. In an interlocking system for railroads, a stretch of track dividedinto a plurality of track sections, two signals one at each end of saidstretch of track for governing traflic in opposite directions thereover,track switches associated With said track sections, means for operatingsaid track switches, control levers for each of said signals, twodirectional stick relays for each of said track sections, one of saidstick relays being for one direction and the other of said stick relaysbeing for the opposite direction, means locking each of said trackswitches when either one of said directional stick relays for thecorresponding track section is deenergized, and means clearing one ofsaid signals only when the corresponding control lever is operated andthe directional stick relays for the corresponding direction aredeenergized.

4. In an interlocking system for railroads, the combination with a tracklayout, of a plurality of track switches to establish a large number oftrackway routes, switch-position contacts associated with each of saidtrack switches having circuit closing positions corresponding to thepositions of their track points, switch machines for operating each ofsaid track switches, means for manually governing said switch machines,means for preventing said manual governing means from causing operationof said switch machines, lock contacts associated with each of saidtrack switches having circuit closing positions assumed when theircorresponding switch machines are locked against operation, wiresconnecting said switch-position contacts and said lock contacts toestablish route circuits corresponding to the trackway routesestablished by said track switches, a signal at each end of a trackwayroute, energizing means at each end of each route circuit forenergizingthe particular route circuit then established, interlocking means forpreventing the energizing means at Cil one end of a route circuit fromfunctioning when the energizing means at the other end of said routecircuit is efie'ctive, and a signal control circuit governed jointly bysaid energizing means and its associated interlocking means..

5. In an interlocking system for railroads, 'a track layout including aplurality of track switches to establish a large number of trackwayroutes, contacts associated with said track switches having circuitclosing positions corresponding to the positions of their track points,

wires connecting said contacts to establishroute circuits correspondingto the trackway routes established by said track switches,-a signal ateach end of each trackway route, energizing means at each end of eachroute circuit for energizing such route circuit when established,interlocking means for preventing the energizing means at one end of aroute circuit from functioning when the energizing means at the otherend of said route circuit is effective, a signal control circuit foreach 01 said signals governed jointly by its corresponding energizingmeans and its associated interlocking means, and means preventing theestablishment, of any route circuit until all of the track switches inthe corresponding trackway route are locked against operation. 7

6. In an interlocking system for railroads, a track layout including aplurality of track switches to establish a large number of trackwayroutes, contacts associated with said track switches having circuitclosing positions corresponding to the positions of their track points,

wires connecting said contacts to establish route circuits correspondingto trackway routes established by said track switches, a signal at eachend of each trackway route, manually governable energizing control meansat each end of each route circuit'for energizing such route circuit whenestablished, interlocking means for reventing the manually governableenergizing control means at one end of a route circuit from functioningwhen the manually governable energizing control means at the other endof said route circuit is effective, signal control circuits for each ofsaid'signals governed jointly by its corresponding manually governableenergizing control means and its associated interlocking .means, meanspreventing the establishment of any route circuit until all of the trackswitches in the corresponding trackway route are locked againstoperation, and means made eilective by each of said manually governableenergizing cohtrol means for effecting the locking of each throw circuitcontroller for each track switch assuming a position corresponding tothe posi tion of such track switch, and a back contact of .the lockrelay associated with each such track switch; and a signal at each endof each route controlled by the route circuit corresponding to suchroute. 7

8. In an interlocking system, the combination with a track layoutincluding a plurality of track switches and track sections associatedwith such .track switches to facilitate tthe establishment of apluralityof routes, switch contacts for each track switch to manifest theposition assumed by suchswitch, a lock relay for each track switch whichif deenergized prevents power operation of such switch, a route circuitfor each of said routes including switch contacts of the trackswitchesincluded in said route and also including' back contacts of thelock relay of each switch included in such route, and means forenergizing such route circuit by current of a character depending on thedirection in which 9. In an interlocking system, the combination with atrack layout including a plurality of track switches and track sectionsassociated with such track switches to facilitate the establishment of aplurality of routes, switch contacts for each track switch tormanifestthe position assumed by such switch, a lock relay for each track switchwhich if deenergized prevents power operation of such switch, a routecircuit for each of said 7 traffic shall be permitted to move over saidroute.

routes including switch contacts of the track manually controllable fordeenergizing the lock relays associated with the track switches of a setup route.

10. In an interlocking system, the combination with a track layoutincluding a plurality of track switches and track sections associatedwith such track switches to facilitate the establishment of a pluralityof routes, switch contactsfor each track switch to manifest the positionassumed by such switch, a lock relay for each track switch which ifdeenergized prevents power operation of such switch, a route circuit foreach of said routes including switch contacts of the track switchesincluded in said route and also including back contacts of the lockrelay of each switch included in such route, means for energizingsuchroute circuit by current of a character depending on the direction inwhich traffic shall be permittedto move over said route, meanscontrolled by the points of the track switches in a set up route forselecting the lock relays of such track switches, and manually operablemeans for deenergizing said selected lock relays, whereby a routecircuit may be closed manually as soon as the route it represents hasbeen set up.

7 l1. Inan interlocking system, the combination with a track layoutincluding a plurality of track switches and track sectionsassociatedwith such track switches to facilitate the establishment of a pluralityof routes, switch contacts for each track switch to manifest theposition assumed by such switch, a lock relay for each track switchwhichif deenergized prevents power oper ation of such switch, a routecircuit for each of said routes including switch contacts of the trackswitches included'in said route and also including back contacts of thelock relay of each switch included in such route, means controlled bythe points of the track switches of a set up route for selecting thelockrelays of such track switches, a signal for governing trafiic over a setup route, and manually operable means for initiating the clearing ofsaid signal in response to closure of such route circuit and fordeenergizing the selected lock relays.

12. In an interlocking system, the combination with a track layoutincluding a -plurality of track switches and track sections associatedwith such track switches to facilitate the establishment of a pluralityof routes, switch contacts for each track switch to manifest theposition assumed by such switch, a lock relay for each track switchwhich if deenergized prevents power operation of such switch, a routecircuit for each of said routes including switch contacts of the trackswitches included in said route and also including back contacts of thelock relay of each switch included in such route, means controlled bythe points of the track switches in a set up route for selecting thelock relays of such track switches, and

manually operable means for deenergizing said selected lock relays,whereby a route circuit may be closed manually as soon as the route itrepresents has been set up.

13. In an interlocking system, the combination with a track layoutincluding a plurality of track switches and track sections associatedwith such track switches to facilitate the establishment of a pluralityof routes, switch contacts for each track switch to manifest theposition assumed by such switch, a lock relay for each track switchwhich if deenergized prevents power operation of such switch, a routecircuit for each of said routes including switch contacts of the trackswitches included in said route and also including back contacts of thelock relay of each switch included in such route, means controlled bythe points of the track switches in a set up route for selecting thelock relays of such track switches, manually operable means fordeenergizing said selected lock relays, whereby a route circuit may beclosed manually as soon as the route it represents has been set up, anda signal controlled by suchroute circuit.

14. In combination, a stretch of track, a trafiic device included withinsaid stretch of track and operated for at times breaking the continuityof said stretch of track, signals at opposite ends of said stretch forgoverning trafiic in both directions over said stretch of track, acircuit extending between two traffic governing relays respectivelyassociated with the opposite ends of said stretch of track, a currentsource at each end of said circuit for supplying current to said circuitbut normally disconnected therefrom, a manually controlled relayassociated with each end of said circuit, a contact included in saidcircuit which contact is closed only when the continuity of said stretchis completed by said traific device, a second contact included in saidcircuit which second contact is closed only when said traffic device islocked to prevent its operation, means governed by each said manuallycontrolled relay when energized to connect the associated current sourcewith said circuit, means for clearing the one of said signalsat the endof said stretch having both its associated said traflic governing relayand said manually controlled relay energized so as to permit trafiic tomove through said stretch of track in a direction determined by the endat which said circuit is supplied with current, and means effective uponthe energization of any one of said manually controlled relays forclosing said second contact.

15. In combination, a stretch of railway track, a power operated trackswitch included in said stretch, a trafiic governing circuit connectingtwo trafiic governing relays respectively associated with opposite endsof said stretch and which circuit is normally short circuited, a switchposition reflecting contact included in said traffic governing circuitand closed only when said stretch of track is continuous, a lock contactincluded in said traflic governing circuit and closed only when saidpower operated track switch is locked to prevent its operation, a sourceof current associated with each end of said traffic governing circuitfor applying current to said circuit but both normally disconnectedtherefrom, a signal normally indicating stop located at each end of thestretch to govern trafiic 1 through said stretch in opposite directions,a control circuit for each signal having two normally open contacts, afirst circuit controller governed from a central dispatching office forclosing one of said contacts for the control circuit of a signal, asecond circuit controller governed from the central dispatching oflicefor removing the short circuit of the trafiic governing circuit and forconnecting therewith the current source associated with the direction oftrafiic governed by said signal and for energizing the trafiic governingrelay associated with that direction of traific, means governed from thecentral dispatching office for closing said lock contact,

and means controlled by said traflic governing relay when energized toclose the other contact of the control circuit for said signal, wherebyonly the signal for a particular direction can be cleared at the sametime, and whereby any particular signal cannot be cleared unless saidpower operated track switch is locked.

16. In an interlocking system for railroads; a stretch of railway track;a plurality of track switches in said stretch of track; a power operatedswitch machine for operating each of said track switches; switch controlcircuits for controlling said switch machines; signals for governingtraffic over said stretch of track and said track switches in eitherdirection; signal control circuits for controlling said signals;manually governed means for controlling said switch and signal controlcircuits; an electro-responsive locking means having front and backcontacts of which the front contacts are rendered effective upondeenergization thereof and opening of such front contacts to preventoperation of their switch machines, said locking means being deenergizedin response to actuation of said manually governed means to a conditionto cause a signal to tend to indicate proceed; and means including backcontacts of said locking means for electrically interlocking said trackswitches and signals so that said signals can be caused by said manuallygoverned means through their respective control circuits to displayproceed indications only when said locking means is rendered effectiveand said back contacts are closed, so that all of said switch machinesare prevented from operating through their respective control circuits,and so that signals for governing traific in one direction only can becaused to display proceed indications.

EDWIN C. LARRY. ANDREW LANGDON.

